Not to rain on your parade, but anything new that you buy for that money can be pretzeled by your tractor.

At best you will need to spend about $1000 for a manual operated rear blade, and you might have to be careful with that. You need to look for a used one to get close to your price range and then most likely it will still be to light duty for you.
I made the mistake of spending around $1k for my first rear blade.

Don't get me wrong, it was an ok blade for a 50hp tractor. But I have a 75hp tractor and I bent it the very first time that I used it. Warranty said that it was abused and would not cover the damage,

I continued to use it and it continued to bend.

Ended up getting a $4k Land Pride blade,
now it is one nice blade.
When it comes to implements and attachments, you usually get what you pay for.

Oh, I would highly consider an 8 foot blade for your tractor.
Good luck